"Why we've continued on is a more interesting question. The more you do, the harder it is to exit."

El-Erian agrees with Fed chair nominee Janet Yellen that the best way to escape from easing is with strong economic growth.

"So the whole system now has bet on the effectiveness of QE, not in terms of asset prices —
we know that works — but in terms of ultimately delivering growth." By "asset prices" he was referring to the rise of stocks to record highs.

So it's economic growth, "if it comes, that what will validate [stock] market pricing. Otherwise, the convergence happens the other way around." In other words, a weak economy would ultimately lead to a weak stock market.

Various commentators have pointed out that the stock market's rally, largely credited to the Fed's easing, is disproportionately benefiting the wealthy.

A distinction must be made between "the asset channel [financial markets] that benefits the rich and the credit channel [lending] that benefits society more broadly," El-Erian said. "The problem is, we haven't unclogged the credit channel."

QE, or at least the talk of the Fed's tapering of QE, is having negative effects overseas, hurting emerging markets in particular by roiling their financial markets.

"Could QE here benefit the U.S. while breaking something outside that feeds back into the U.S.? That is going to become more interesting in the months ahead. We're complicating the life of policymakers" overseas, El-Erian said.

"Look at Brazil, Indonesia. They're finding it very hard to deal with the spillover effects of QE." Both countries have been hit with currency weakness amid talk that the Fed will taper.

El-Erian offered words of praise for Yellen. "This is a really hard job, and we've got a very qualified person who's going to take over the job from Ben Bernanke," he said. "So thank God she's doing it, and we wish her well, because there's a lot at stake."

Fiscal policy won't offer Yellen any help, El-Erian says. "What we need is the political system to come together and engage policy-making entities that have better suited tools," he said.

"Is it going to happen? No. The result of that is that the Fed will keep its foot on the accelerator. It will continue with its stimulus. It will tweak it over time — a bit less QE, a bit more forward guidance." By "forward guidance" El-Erian means a pledge by the Fed to keep interest rates low.

The Fed will hope that growth then materializes, he says. "It's really a big question mark whether it does."

Former Fed Gov. Kevin Warsh also sees the outcome of QE as a big question mark. The turmoil surrounding possible tapering "should correct the misimpression that QE is anything other than an untested, incomplete experiment," he wrote in The Wall Street Journal.